import * as Cesium from 'cesium';
import 'cesium/Build/Cesium/Widgets/widgets.css';

const viewer = new Cesium.Viewer('root');
const provider = await Cesium.TileMapServiceImageryProvider.fromUrl(
   CESIUM_MAP_SOURCE_URL,
   {
      fileExtension: 'png',
      maximumLevel: 4,
      rectangle: new Cesium.Rectangle(
         Cesium.Math.toRadians(-120.0),
         Cesium.Math.toRadians(20.0),
         Cesium.Math.toRadians(-60.0),
         Cesium.Math.toRadians(40.0)
      ),
   }
);
const imageryLayer = new Cesium.ImageryLayer(provider);
viewer.imageryLayers.add(imageryLayer);
